{{Short description|Extinct family of trilobites}} {{Automatic taxobox | fossil_range = {{fossil range|Late Cambrian|Early Ordovician}} | image = Entomaspis_radiata.JPG | image_caption = ''Entomaspis radiata'' | taxon = Entomaspididae | authority = Ulrich, 1931 | subdivision_ranks = Genera | subdivision = * ''Baikadamaspis'' * ''Entomaspis'' * ?''Hypothetica'' }}
'''Entomaspididae''' is a family of harpetid trilobites that ranges from the Upper Cambrian to Lower Ordovician of marine strata in China and the United States.<ref name='Treatise'>{{cite book|last= Moore|first= R.C.|year= 1959|title= Arthropoda I - Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha|publisher= Geological Society of America/University of Kansas Press|series= Treatise on Invertebrate Paleontology|volume= Part O.|pages=1–560, 419|location= Boulder, Colorado/Lawrence, Kansas|isbn= 0-8137-3015-5}}</ref>
== Description == Entomaspidids, as in other harpetid trilobites, have proportionally large, vaulted cephalons, shaped like croissants or bonnets, with the cheeks freed to be modified into long and curved spines in ''Entomaspis'' and ''Hypothetica''. Although the eyes of Entomaspididae are small compared to many other trilobites, the eyes are large when compared to other harpetids bearing eyes. Entomaspidids can be further distinguished from other harpetids by having a continuous border along the rim of the pygidium composed of small, stub-like spines.<ref name=Suzuki>Suzuki, Yutaro. "Systematic position and palaeoecology of a cavity-dwelling trilobite, Ityophorus undulatus Warburg, 1925, from the Upper Ordovician Boda Limestone, Sweden." Paleontological research 6.1 (2002): 73-83.</ref> In overall appearance, the typical Entomaspidid is a near-circular, medallion-like trilobite.
== Taxonomy == Entomaspididae is thought to represent the transition between the ancestral Ptychopariida, and the harpetids. Many researchers question the validity of Entompaspididae as a distinct family, and merge its genera into Harpetidae.<ref name=Adrsteph>Adrain, Jonathan M., and Stephen R. Westrop. "Notchpeakia, a new genus of Upper Cambrian (Sunwaptan)“entomaspidid” trilobites." Journal Information80.6 (2006).</ref>
Ulrich erected "Entomaspididae" to contain species of ''Entomaspis'' and ''Hypothetica'', from the Latest Cambrian or Earliest Ordovician of Utah.<ref name='Treatise' />
== Distribution == The first entomaspidids appear in the fossil record near the close of the Cambrian period in marine strata of Utah and China. They persist into the Early Ordovician before disappearing from the fossil record.
== Recognized taxa == The three genera traditionally placed in Entomaspididae include the type genus, ''Entomaspis'', whose species are found in Utah and Missouri, and ''Hypothetica'', which lived sympatrically with Utah species of ''Entomaspis'', and ''Baikadamaspis'', of Late Cambrian marine strata in China. Many authorities merge ''Hypothetica'' into ''Entomaspis''.
==References== {{Reflist}}
{{Taxonbar|from=Q22285129}}
Category:Harpetida Category:Trilobite families Category:Cambrian first appearances Category:Early Ordovician extinctions